While the designation applies to the complete system, it also commonly used in reference to the pistol component itself. The pistol itself, chambered for the .45 ACP cartridge, was developed by Heckler & Koch, and was selected over the Colt OHWS through USSOCOM's Offensive Handgun Weapon System (OHWS) program. The initial LAM and suppressor were developed by Insight Technology and Knight's Armament Company (KAC), respectively.

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The Mk 23 Mod 0 was built as an "offensive" handgun for special operations forces under USSOCOM, as per request made in 1989. Military versions of the weapon have the writing "MK23 USSOCOM" engraved on the slide.

The Mk 23 is considered a match grade pistol, and is capable of making a 2 inch group at 50 yards, roughly 4 MOA. Production began in 1991, and it was the basis for the HK USP, which began production in 1993. The MK23 has exceptional durability in harsh environments, being waterproof and corrosion-resistant. It uses a hexagonal barrel design, which is reported to improve accuracy and durability. It also features an ambidextrous safety and magazine release on both sides of the frame. The magazine release is at the rear edge of the trigger guard, which is wide enough to allow the use of gloves. A decocking lever is on the left side, which will silently lower the cocked hammer. The U.S. Navy MK23 is part of a larger weapon system that includes an attachable laser aiming module, a suppressor, and some other features such as a special high-pressure match cartridge (.45 +P ammunition).

The weapon was tested and found to be capable of firing tens of thousands of rounds without a barrel change. It remains reliable in harsh conditions, making it suitable for use by special forces.

However, the weapon's large size and weight have resulted in some criticism. In response, HK developed the USP Tactical pistol based on the original USP; the Tactical retains much of the performance of the MK23 without the bulky size, and is able to use the suppressor though not the LAM. An even more compact pistol than the USP Tactical for counter-terrorist and special forces use is the new HK USP Compact Tactical, which does have its own optional LAM. The USP-CT is lighter and is capable of fitting a silencer, making it a prime choice for Special Forces on covert operations.

The proposed Joint Combat Pistol (JCP) was intended to accept match grade and +P ammunition. However, it is not clear if the JCP, which absorbed the earlier SOF Combat Program, will be used alongside or replace the MK23 handguns. As of 2006, the JCP has since been renamed and restructured.

The MK23 was submitted to the USSOCOM Offensive Handgun Weapon System (OHWS) competition around late 1991 the goal of which was to create an entire pistol package capable of replicating the performance of longer barreled weapons such as submachine guns with many customizable features. Its rival was the Colt OHWS. Though both Heckler & Koch's and Colt's designs were tailored to the demanding requirements of the OHWS competition, the MK23 eventually won.

HK commercially markets the MK23 and derivatives of it, but not the complete SOCOM system. The suppressor is made by Knight's Armament Company, and was selected over the one HK originally included as part of its entry. Insight Technology won the contract to produce the laser aiming module, later designated AN/PEQ-6. One version of the LAM produces a visible light dot, while another produces an infrared dot that can only be seen through night vision goggles. There have since been different LAM models and, at least commercially, different suppressors as well.

The first MK23 production models were delivered to SOCOM on May 1, 1996. At last count, 1,986 models were built (serial numbers 23-0101 through 23-2086).

Heckler & Koch is offering the MK23 on the civilian market as the Mark 23. It is distributed by its subsidiaries HK Inc. (United States) and HKJS GmbH (Germany).

The models for the U.S. market initially came with a 10-round magazine, to comply with the U.S. Assault Weapons Ban. The ban has now expired, and the civilian Mark 23 comes with the same 12-round magazine as the government variants. In Canada, the Mark 23 pistol is still supplied only with 10-round magazines, as per the 1995 Firearms Act.

According to the Operators Manual,[1] there are few differences between the civilian Mark 23 and the government MK23. These differences are the slide engraving ("Mark 23" instead of "MK23 USSOCOM") and a barrel conforming to SAAMI headspace specifications.